What TETRA & TETRAPOL mean? What are the difference?

Both names refer to standards used in radio communications. TETRA is a global standard that runs on a TDMA in which a frequency may carry multiple radio channels that are temporally multiplexed.

TETRAPOL is a standard that was developed by EADS (formerly Matra Communications) which is used across European countries but more particularly in France by firefighters and police. This standard is based on the use of a frequency for a single radio channel.

These two types of radio standards have their advantages and disadvantages (speed + important for TETRA, greater scope for TETRAPOL), but currently, worldwide, TETRA is the most used.